CN105848398B

CN105848398B - Plasma torch

Info

Publication number: CN105848398B
Application number: CN201610066911.3A
Authority: CN
Inventors: 弗兰克·劳里施; 蒂莫·格伦德克; 雷内·诺戈夫斯基; 沃克·克林克
Original assignee: Kjellberg Stiftung
Current assignee: Kjellberg Stiftung
Priority date: 2015-01-29
Filing date: 2016-01-29
Publication date: 2020-05-15
Anticipated expiration: 2036-01-29
Also published as: BR102016001981A2; PL3051928T3; EP3051928A1; CA2917397C; US20160227640A1; CA2917397A1; ES2717509T3; CN105848398A; US9743505B2; RU2705048C2; EP3051928B1; RU2016101050A3; BR102016001981B1; KR20160093546A; KR102542212B1; RU2016101050A

Abstract

The present invention relates to a plasma torch, preferably a plasma cutting torch, wherein plasma gas PG1 and/or plasma gas PG2 flows through at least one feed, through the housing of the plasma torch, to the nozzle opening. A hollow space connected to the feed section is also present in the housing, at the opening of which a valve is arranged that opens and closes the opening, in the open state of which valve it is possible to achieve that plasma gas PG1 and/or plasma gas PG2 leaving the feed section to the nozzle opening is guided out.

Description

Plasma torch

Technical Field

The present invention relates to a plasma torch, and in particular to a plasma cutting torch.

Background

Plasma is a high temperature heated conductive gas composed of cations, anions, electrons, and excited neutral atoms and molecules. Various gases (e.g., monatomic argon and/or diatomic gases hydrogen, nitrogen, oxygen, or air) are used as the plasma gas. These gases are ionized and dissociated by the energy of the electric arc. The arc confined by the nozzle is hereinafter referred to as a plasma jet. The design of the nozzle and the electrodes greatly affects the parameters of the plasma jet. Such parameters of the plasma jet are, for example, the jet diameter, the temperature, the energy density and the flow rate of the gas.

In plasma cutting, the plasma is typically confined by a nozzle, which may be air or water cooled. Thereby, up to 2 x 10 can be realized⁶W/cm²The energy density of (1). The temperature rises in the plasma jet up to 30000 ℃, which in combination with the high flow rate of the gas can have a very high cutting speed on the material.

A plasma torch generally includes a plasma torch head and a plasma torch shaft. The electrode and the nozzle are secured in a plasma torch head. The plasma gas flows between them and out through the nozzle hole. A gas guide is attached between the electrode and the nozzle and may be arranged to rotate, through which the plasma gas is typically guided.

Such arrangements are also known: a valve (preferably a solenoid valve) switches or regulates the plasma gas. They are located outside the torch shaft/torch housing in the assembly. For example, the valves may be secured in the assembly at the hose pack. It is also known that these valves are attached to a coupling unit between the gas hose of the plasma torch and a supply hose for the gas supply.

It is also known to use a plurality of valves for the plasma gas. For example, they are gases for ignition and gases for cutting. Oxygen is used as the plasma gas for plasma cutting. The plasma may be ignited with air or nitrogen, and the cutting may be performed with oxygen. There is also the possibility of mixing gases, for example argon and hydrogen, in the cutting of alloy steels. It is also known that, in order to change between different plasma gases as quickly as possible, the respective hose line should be vented.

In the known solutions it is disadvantageous that a fast switching between gases and a fast venting of the plasma gas space in the interior of the plasma head/housing, the volume of which is formed by the pipe or the bore or in another way between the nozzle bore and the valve, is not possible in a sufficiently short time. In particular, with a nozzle orifice of smaller diameter, it may take several 100ms, partly even up to 1 second, before the pressure in the space is reduced below 0.5 bar. During shutdown, it is often desirable to shut off the plasma arc at the end of the cut at the pressure of plasma gas PG1 or at the pressures of plasma gases PG1 and PG2, the pressure of plasma gas PG1 or at the pressures of plasma gases PG1 and PG2 being as low as possible to minimize electrode wear. Furthermore, one additional disadvantage is that the length of the line affects the time until the desired reduced pressure has been reached. Long line lengths extend time but are frequently necessary due to different kinds of guiding systems, such as robotically controlled or CNC controlled xy-guided machines with and without pivoting units for bevel cutting.

The attachment of the valve to the plasma torch shaft is disadvantageous for fastening in the guide system; especially due to the pivoting unit.

Disclosure of Invention

It is therefore an object of the present invention to provide a possibility for improving the conditions of shutdown, switching or change in the control operation or regulation operation of a plasma torch supplying plasma gas.

According to the invention, this object is achieved by a plasma torch having the features of the invention. Advantageous embodiments and further developments of the invention can be realized with the features specified in the invention.

In a plasma torch according to the present invention, plasma gas PG1 is directed through at least one feed and/or through a housing of the plasma torch and through a hollow space formed within the housing and communicating with or connected to the nozzle opening. At least one valve for opening and closing the respective feed may be present in at least one feed. These valves for opening and closing the feed may be arranged outside and/or inside the plasma torch.

A hollow space having an opening is formed in the housing in such a manner as to be connected to the feeding portion. The opening should preferably be directed outwards outside the housing. A valve that opens and closes the opening is disposed at the hollow space within the housing. In certain operating states, in particular changes of operating state, the plasma gas leaving the feed to the nozzle opening can be conducted out via this opening with the valve open.

Since the opening can be led outwards out of the housing (optionally via a further line), it can in the simplest case simply communicate with the environment when the valve connected to the opening is opened. However, it can also be connected to a unit for generating vacuum and/or to a container in which the pressure is maintained below the pressure in the feed, preferably below the pressure in the region before the nozzle opening and below the ambient pressure.

At least one pressure sensor may be arranged in or connected to at least one feed and/or hollow space, with which preferably the current and/or voltage and/or the gas itself with which the operation of the plasma torch can be controlled and/or regulated. The pressure and/or the volume flow of the supplied plasma gas or auxiliary gas can be controlled or adjusted individually or additionally as a function of the pressure determined in this way.

There is also the possibility that a further feed for the auxiliary gas SG is guided through the housing. The auxiliary gas SG can be conducted to the outside by means of the nozzle-protecting cap and an auxiliary gas feed formed in the nozzle-protecting cap close to the plasma jet which emerges through the nozzle opening. The valves for opening and closing should likewise be connected to the auxiliary gas feed.

Preferably, the valves for the supply of plasma gas and optionally for the auxiliary gas should be able to be adjusted or controlled.

In addition to the valves present at or at the hollow space, at least one valve for opening and closing the feed for plasma gas PG1 and/or PG2 may also be arranged within the housing, in the flow direction of the respective plasma gas PG1, PG2, before the respective feed is connected to the hollow space. These valves arranged in the housing should preferably be capable of being actuated electrically, pneumatically or hydraulically and should particularly preferably be configured as axial valves. The electrically actuatable valve may be electromagnetically controlled or controlled using the piezoelectric effect.

At least one valve arranged in the housing, i.e. a valve arranged in the feed or at the opening of the hollow space, should have a maximum outer diameter or a maximum average facing angle of 15mm, preferably a maximum of 11mm, and/or a maximum length of 50mm, preferably a maximum of 40mm, particularly preferably a maximum of 30mm, and/or the maximum outer diameter or the maximum average facing angle of the housing should amount to 52 mm. The maximum outer diameter should amount to a maximum 1/4, preferably a maximum 1/5, of the outer diameter of the housing. The valve should have a maximum electrical power consumption of 10W, preferably 3W, particularly preferably 2W.

The average maximum facing angle line can be understood for a rotationally asymmetrical cross section as the average of all facing angle lines of the respective cross section. The given values should apply 1:1 to the outer diameter and for the face angle line the particular value should be up to 15% greater than the given value for the outer diameter.

In an electrically operable valve, the plasma gas (PG1, PG2) or the auxiliary gas should flow through the windings of the coil, whereby cooling is achieved.

The hollow space may have a decreasing free cross section in the flow direction before the valve present at the hollow space. However, a reduced free cross-section may also be present at the opening after the valve in the flow direction. The venting time can be influenced by the free cross section and thus reduced. A membrane reducing said free cross section may also be arranged there. In particular, the time during which the plasma gas can escape with the valve open at the hollow space can be increased by this reduced free cross section or by the diaphragm to ensure that the plasma gas is still present in the space as long as the voltage is still applied to the electrode and/or as long as the current flows through the electrode. Thereby, the lifetime of the electrode can be extended and critical operating states in which the plasma gas escapes very quickly are avoided.

A plasma torch according to the present invention can also be configured as a rapidly changing torch having a plasma torch shaft that is separable from the plasma torch head. Thus, a simple and fast change to the changed desired process conditions or process requirements can be achieved by a simple exchange of components.

If a venting process is to be performed, the valves in the feed for the plasma gas and optionally for the auxiliary gas should first be closed before the valves integrated or arranged in the hollow space are opened. Alternatively in this respect, the valves may be closed simultaneously and the valves integrated or arranged in the hollow space may be opened.

Drawings

The invention will be better explained below with reference to examples. The technical features of the individual embodiments and the different examples can be combined with one another independently of the examples described separately accordingly. In the following drawings:

fig. 1 shows in schematic form a cross-sectional illustration of an example of a plasma torch with a plasma feed according to the invention;

fig. 2 shows in schematic form a cross-sectional illustration of a further example of a plasma torch with a plasma feed according to the invention;

fig. 3 shows in schematic form a cross-sectional illustration of an example of a plasma torch according to the invention with two plasma feeds;

fig. 4 shows in schematic form a cross-sectional illustration of a further example of a plasma torch having two plasma feeds in accordance with the present invention;

fig. 5 shows in schematic form a cross-sectional illustration of an example of a plasma torch according to the invention having a plasma feed and an auxiliary gas feed;

fig. 6 shows in schematic form a cross-sectional illustration of a further example of a plasma torch having a plasma feed and a pressure sensor in accordance with the present invention;

FIG. 7 shows a cross-sectional illustration of an axial valve that may be used in the present invention;

fig. 8 shows a possibility for the arrangement of a valve within the housing of the plasma torch; and

fig. 9 shows a further possibility for the arrangement of the valve within the housing of the plasma torch.

Detailed Description

An example of a plasma torch 1 is shown in simplified form in the accompanying drawings. In addition to the gases, the additional media (e.g., electrical current and cooling water) required to operate the plasma torch 1 and to supply them to the plasma torch 1 are not shown.

Fig. 1 shows a plasma torch 1, which plasma torch 1 has a plasma torch head 2 with a nozzle 21, an electrode 22, and a feed 34 for a plasma gas PG, and a plasma torch shaft 3 with a housing 30. In the present invention, that is to say in all other examples covered by the present invention, the plasma torch shaft 3 may be formed in one piece and may be formed only by one correspondingly configured housing 30, all the necessary components being present and formed at the housing 30.

The feeding portion 34 may be a gas hose outside the housing 30 connected to the magnetic valve 51 of the linkage unit 5 for infeed of the plasma gas PG 1. Another portion of the feed 34 abuts the gas hose and is formed within the housing 30. The feeding portion 34 is connected to the hollow space 11 inside the housing 30. When the valve 33 is opened, plasma gas can escape through the hollow space 11, via an opening which is present at the hollow space 11 and which is arranged behind the valve 33, out of the space 24 formed between the nozzle 21 and the electrode 22 into the environment or into a connected vessel. This may occur through a line 37 after the valve 33. The electrode 22 and the nozzle 21 are arranged at a distance from each other by a gas guide 23, so that a space 24 is formed within the nozzle 21. The nozzle 21 has a nozzle hole 210, and the diameter of the nozzle hole 210 can be changed from 0.5mm for 20A to 7mm for 800A according to the electrical cutting current. The gas guide 23 likewise has openings or holes (not shown) through which the plasma gas PG flows. They may likewise be configured in different sizes or diameters and even different numbers.

A solenoid-operable valve 33 is located in the plasma torch shaft 3 and its gas inlet is connected to the hollow space 11, so that with the valve 33 open, plasma gas can move outwardly out of the housing 30 through the opening out of the hollow space 11 and optionally there into a vessel (not shown) where a vacuum exists. The inner volume of the hollow space 11 is minimized. For example, it amounts to 5cm³To 10cm³. The valve 33 is designed as an axial valve of small constructional shape. For example, it thus has an outer diameter D of 11mm and a length L of 40 mm. For example, a small electric power (here about 2W) is required to reduce the temperature rise of the housing 30.

At the time of arc ignition and during cutting, plasma gas PG1 flows into housing 30 through open valve 51 and feed 34, and from there into hollow space 11.

If the cutting is to be ended, the valve 51 in the coupling unit 5 is first closed. Since the plasma gas PG1 should flow out of the space 24 between the nozzle 21 and the electrode 22 in as short a time as possible to reduce the pressure in this space 24, the valve 53 is opened to exhaust the feed portion 34, and the valve 33 is opened for rapid exhaust of the hollow space 11 and the space 24. Here, the hollow space 11 and the space 24 are connected to each other through an opening or a hole of the feeding portion 34.

In this regard, the plasma gas PG flows through the space of the valve 33 surrounded by the windings of the coil S, thereby better cooling the valve 33. The valve 33 can be arranged in the housing 30 without any further precautions due to the small constructional shape, the required low electrical power and the cooling by the flowing plasma gas.

After the exhaust, the

valves

33 and 53 are closed again and the arc can be ignited again. A short air bleeding time, which hardly depends on the inner diameter of the nozzle hole 210 and the inner diameter of the hole formed in the feeding portion 34 inside the housing 30, can be achieved by this arrangement. In particular, with nozzle bores of 1mm or less, without the described arrangement, the venting time would amount to several 100 ms. In the illustrated embodiment, the venting time may be reduced to below 200 ms.

A short venting time is important to start the next cutting process as quickly as possible to reduce the pause between cutting processes and improve production efficiency. In addition, the rapid pressure reduction extends the useful life of the electrode 22, otherwise the electrode 22 is more worn by erosion after the arc is extinguished at the higher plasma pressure in the space 24 and the associated flow of plasma gases PG1, PG 2.

A further gas hose as a line 37 can be connected to the hollow space 11 and to the opening behind the valve 33 in the flow direction, which gas hose can be used to conduct the plasma gas to be removed out in a defined manner during the venting, so that the plasma gas can be conducted to a specific location, for example to a container (not shown). By way of example, here, in the flow direction, before the gas inlet side E of the valve 33, a diaphragm is attached, with which the plasma gas flows in order to be guided out during the exhaust process and thus the exhaust time can be influenced.

In the present embodiment, the exhaust duration also depends on the length of the total feed 34 (i.e. the length of the feed 34 outside the housing 30) and therefore on the internal volume of the feed. An example of this no longer being the case is shown in fig. 2.

Fig. 2 also shows a plasma torch 1. Before the hollow space 11 is connected to the feed 34, a further valve 31 is additionally located in the feed 34 in the housing 30. The outlet of the valve is connected to the hollow space 11.

A valve 33, the air inlet of which is connected to the hollow space 11, is connected to the hollow space 11 inside the housing 30, or is disposed in an opening connected to the hollow space 11, so that air discharge can be achieved with the valve 33 opened. The internal volume of the hollow space 11 is minimized. The internal volume is limited by the

valves

31 and 32 and by the gas guide 23, which gas guide 23 can be part of the feed 34, and here the internal volume amounts to, for example, 5cm³To 10cm³。

The

valves

31 and 33 are designed as small-form-factor axial valves. For example, they therefore have an outer diameter D of 11mm and a length L of 40 mm. For example, a small electric power (here, about 2W) is required to reduce heat generation of the housing 30.

At the time of arc ignition and during cutting, plasma gas PG1 flows into plasma torch 1 through open valve 51 and feed 34, through valve 31 and from there into hollow space 11.

If the cutting is to be ended, the valve 51 in the coupling unit 5 is first closed. Since the plasma gas PG1 should flow out of the space 24 between the nozzle 21 and the electrode 22 as quickly as possible to reduce the pressure in the space 24 in a short time, the valve 31 is closed and the valve 33 is opened for quick exhaust of the hollow space 11 and the space 24. Here, the hollow space 11 and the space 24 are connected to each other through an opening or a hole of the gas guide 23.

In this respect, the volume of the winding of the

respective valve

31, 33 surrounding its respective electrical coil S is flowed through, whereby it is better cooled. The valve can be arranged in the housing 30 due to its small constructional shape, the small electrical power required and the cooling by the flowing plasma gas.

After the exhaust, the valve 33 is closed again and the arc can be ignited again. An even shorter venting time, which hardly depends on the diameter of the nozzle bore 210, the diameter of the bore in the gas guide 23 and the length of the feed 34, can be achieved by this arrangement. In the illustrated embodiment, the venting time may be reduced to less than 100 ms.

The exhaust valve 53 is provided in the coupling unit 5. This is necessary if the total feed 34 should vent up to the valve 31. This is useful, for example, when different pressures are required for plasma gas PG1 between cutting processes. However, this arrangement can also be used generally without the

valves

51 and 53. Rapid degassing of the hollow space 11 and the space 24 is thereby also possible.

Due to the even shorter venting time, the next cutting process can be started even faster. Additionally, the reduction in internal pressure that can be achieved in even shorter times extends the useful life of the electrode 22.

However, in the case of a large nozzle, merely closing the valve 31 is sufficient for venting, without opening the valve 33, after which the plasma torch is operated in a conventional manner.

The parameters of the respective cut may be stored in a database and may define a program of whether and when the valve 33 is opened. The same may be provided that the diaphragm 38 is arranged before the gas inlet (e.g. between the hollow space 11 and the valve 33) or at the gas outlet of the valve 33 or after the gas outlet of the valve 33, the diaphragm 38 having an inner diameter smaller than the smallest inner diameter of the valve 33 through which the plasma gas flows. This can likewise influence the venting time. It is equally possible that the free cross-section of the diaphragm 38 through which plasma gas can flow is variable. In addition, a further line 37 may be connected to the valve 33 and/or to the diaphragm 38, so that the plasma gas may escape to a specific location (for example out of the housing 30), here for example to the coupling unit 5. Openings through which plasma gas may escape may equally exist in the housing 30. This also applies to the examples shown in fig. 1 and 3.

It is useful for certain applications, for example, to supply two plasma gases PG1 and PG2 to the plasma torch 1 when ignition should be performed with one plasma gas and cutting with another plasma gas. For example, ignition is performed with air and cutting with oxygen to reduce electrode wear. There is also the possibility of mixing two different plasma gases in the plasma torch 1 or switching in a second plasma gas during the cutting process. This is useful, for example, when cutting with an argon-hydrogen mixture. Where ignition is performed with argon, after which hydrogen is mixed. However, here switching between two plasma gases is equally possible; for example, ignition is performed under argon as the plasma gas PG1, followed by switching to the plasma gas PG2, argon-hydrogen mixture, or argon-nitrogen mixture, or argon-hydrogen-nitrogen mixture that has been mixed. An arrangement is shown by way of example in fig. 3 for this purpose.

Likewise, fig. 3 shows a plasma torch 1. Before being connected to the hollow space 11 in the direction of flow, a respective valve 31 and a further valve 32 are connected within the housing 30 or are arranged there in the feed 34 and the feed 35 for different plasma gases. The inlet of the valve 31 is connected to the feed 34 and the inlet of the valve 32 is connected to the feed 35. The air outlets of both

valves

31 and 32 are connected to the hollow space 11.

A valve 33 with an inlet connected to the hollow space 11 is located in the housing 30 so that it can vent the hollow space 11. The internal volume of the hollow space 11 is minimized. The volume to be evacuated is also limited in a certain manner by the volumes of the

valves

31 and 32 and the gas guide 23, and for example, here, the volume to be evacuated amounts to 5cm³To 10cm³。

The

valves

31, 32 and 33 are designed as small-form-factor axial valves. For example, it thus has an outer diameter D of 11mm and a length L of 40 mm. For example, they require a small electrical power (here about 2W) in order to reduce heating in the housing 30.

At the time of arc ignition and during the maintenance of the arc (arc combustion between electrode 22 and nozzle 21), plasma gas PG1 flows through open valve 51 and feed 34 to plasma torch 1, through valve 31 and from there into hollow space 11.

During cutting, i.e. in particular when the arc is burning, plasma gas PG2 flows in the direction of the workpiece through open valve 52 and feeds into plasma torch 1, through valve 32, flowing between electrode 22 and nozzle 21.

Here, for example, there is a case as has been described previously in which switching is performed between two different plasma gases PG1 and PG2 or a second plasma gas PG2 is switched in. In the first case, the valve 31 is closed and the valve 32 is open. Valve 51 may be closed, valve 52 must be opened, and only plasma gas PG2 flows. This may also occur in an overlapping manner, i.e. both valves are open for a certain time (e.g. 300ms) to ensure a constant gas flow.

In the second case, where cutting is performed with two plasma gases (e.g., with a gas mixture), plasma gas PG1 and plasma gas PG2 flow into nozzle 21.

If the cutting is to be ended in the first case, the valve 52 in the coupling unit 5 is first closed. Since the plasma gas PG2 should flow out of the space 24 between the nozzle 21 and the electrode 22 as fast as possible to reduce the pressure in this space 24 in a short time, the valve 32 is closed and the valve 33 is opened for rapid venting of the hollow space 11 and the space 24. Here, the hollow space 11 and the space 24 are connected to each other through an opening or a hole of the gas guide 23.

If in the second case the cutting is to be ended, the

valves

51 and 52 in the coupling unit 5 are first closed. Since the plasma gas PG1 and the plasma gas PG2 should flow out of the space 24 between the nozzle 21 and the electrode 22 as quickly as possible to reduce the pressure in the space in a short time, the

valves

31 and 32 are closed and the valve 33 is opened for the evacuation of the hollow space 11 and the space 24 in a short time. Here, the hollow space 11 and the space 24 are connected to each other through an opening or a hole of the gas guide 23.

In this respect, the volume of the

respective valve

31, 33 surrounding the windings of its respective coil S is flowed through, as a result of which it is cooled better. The valve can be arranged in the housing 30 without any further additional measures due to the small constructional shape, the small electrical power required for operation and the cooling by the flowing plasma gas.

After the exhaust, the valve 33 is closed again and the arc can be ignited again. An even shorter venting time, which hardly depends on the diameter of the nozzle bore 210, the diameter of the bore in the gas guide 23 and the length of the feed 34, can be achieved by this arrangement. In this example, the exhaust time may be reduced to below 100 ms.

The discharge valve 53 and the discharge valve 54 are provided in the coupling unit 5. This is necessary even though feed 34 should also vent upward to valve 31 and feed 35 for second plasma gas PG2 should also vent upward to valve 32. This is useful, for example, when different pressures for plasma gas PG1 and plasma gas PG2 are required between cutting processes. However, this arrangement can also be used generally without the

valves

51 and 53. Thereby, the evacuation of the hollow space 11 and the space 24 can be realized in a short time.

The following possibilities also exist: only the

valves

31, 32 and/or 33 arranged in the plasma torch shaft are present, the other valves being absent or only partly present. This is shown by way of example in figure 4.

Fig. 5 shows a plasma torch 1, which plasma torch 1 has, for example, a feed 36 for an auxiliary gas SG (as shown in DE 102004049445B 4) in addition to a plasma gas or plasma gas PG1 and a plasma gas PG 2. The plasma torch 1 also has a nozzle-protecting cap 25 and the secondary gas SG flows through the space 26 between the nozzle 21 and the nozzle-protecting cap 25 and can flow around the space 26 or also restrict the space 26, the nozzle-protecting cap 25 fixing the nozzle 21 in the direction of the arc.

The assist gas SG is supplied to the plasma torch 1 through the feeding portion 36. The valve 55 switches and influences the secondary gas SG. As for the valves for plasma gas PG1 and plasma gas PG2, a valve (not shown) for the auxiliary gas SG may also be present in the housing 30.

The plasma torch 1 can also be configured as a fast-changing torch, wherein the torch head can be separated from the torch shaft by simple manual manipulation or in an automated manner, for example as described in DE 102006038134B 4.

Fig. 6 shows the arrangement shown in fig. 2. Also in this respect, a pressure sensor 39 is located in the housing 30 and determines the pressure in the hollow space 11. The measurement results can be transmitted to a control unit, so that the control of the electrical cutting current or the switching of the valve can be carried out as a function of the respective determined pressure. The current may be varied according to the corresponding determined pressure. For example, the current may increase when the corresponding specific pressure increases, and likewise, the current may decrease when the corresponding specific pressure decreases. The dependency may be proportional or non-proportional, following other mathematical functions. Likewise, the current may be switched off when the pressure in the respective determined hollow space 11 falls below a predetermined value.

Fig. 7 shows a greatly simplified design of an axial solenoid valve that can be used in the present invention. A coil S having windings through which plasma gas can flow from the gas inlet B to the gas outlet a is located inside its body. A mechanism for opening and closing is also arranged inside. The body of the solenoid valve has a length L and an outer diameter D. The solenoid valve shown here has a length L of 25mm and a diameter of 10 mm.

Fig. 8 shows a possible space-saving arrangement of the

valves

31, 32 and 33, which are arranged in the housing 30 so that they are each arranged at an angle α 1 of 120 deg. in a plane perpendicular to the centre line M, a deviation from this angle should not exceed + -30 deg. whereby the arrangement saves space and can be arranged in the housing 30 or in the plasma torch shaft 3, the distances L1, L2 and L3 between the

valves

31, 32 and 33, respectively, are ≦ 20mm, at least one of the

valves

31, 32 and 33 is arranged with its inlet E opposite to the other valves, i.e. opposite to their outlet a, in the shown example, the oppositely arranged valve is the valve 33 in the hollow space 11.

Fig. 9 shows an arrangement with four

valves

31, 32, 33 and 40, which are arranged inside the housing 30 so that they are arranged in a plane perpendicular to the centre line M at angles α 1, α 2, α 3, α 4 of 90 ° respectively, the deviation from these angles should not exceed ± 30 °, whereby the arrangement saves space and can be arranged in the housing 30 or in the plasma torch shaft 3, the distances L1, L2, L3 and L4 ≦ 20mm, at least one of these

valves

31, 32, 33 and 40 being arranged with its gas inlet E opposite to the other valves (i.e. opposite to their gas outlet a).

List of reference numerals:

1 plasma torch

2 plasma torch head

3 plasma torch shaft

5 coupling unit

11 hollow space

21 nozzle

22 electrode

23 gas guide

24 space (between electrodes/nozzles)

25 nozzle protective cap

26 space (nozzle-nozzle protective cap)

30 plasma torch shaft housing

31-valve PG1

32-valve PG2

33 exhaust valve

34 feeding section PG1

35 feeding section PG2

36 feeding part SG

37 pipeline

38 diaphragm

39 pressure sensor

40 valve for SG

51 valve

52 valve

53 valve

54 valve

55 valve

210 nozzle hole

A air outlet

D diameter

E air inlet

Length of L

PG1 plasma gas 1

PG2 plasma gas 2

SG assist gas

S coil

L1-L4 valve distance

α 1 angle- α 4 angle

Claims

1. A plasma torch, wherein plasma gas (PG1, PG2) is conducted through at least one feed (34, 35), through a housing (30) of the plasma torch (1), to a nozzle opening (210), and wherein at least one valve (31, 32, 51, 52) for opening and closing the respective feed (34, 35) is present in the at least one feed (34, 35),

a hollow space (11) connected to the feed section (34, 35) being present within the housing (30), a valve (33) opening and closing an opening being arranged at the opening at the hollow space, it being possible to achieve, in the open state of the valve (33) at the opening of the hollow space, an out-guiding of plasma gas (PG1, PG2) exiting the feed section (34, 35) to the nozzle opening (210),

wherein the opening at the hollow space (11) is directed outwards out of the housing (30) and connected to the environment or to a container and/or a unit generating a vacuum, the pressure in the container being maintained below the pressure in the at least one feed (34, 35) in the area before the nozzle opening (210).

2. The plasma torch of claim 1, wherein the plasma torch is a plasma cutting torch.

3. The plasma torch of claim 1, wherein the pressure in the vessel is maintained below ambient pressure.

4. Plasma torch according to claim 1, characterized in that at least one pressure sensor (39) is arranged within the at least one feed (34, 35), a space (24) formed between a nozzle (21) and an electrode (22) of the plasma torch (1), and/or the hollow space (11), or, at least one pressure sensor (39) is connected to the at least one feed (34, 35), the space (24) formed between the nozzle (21) and the electrode (22) of the plasma torch (1), and/or the hollow space (11), with which the current, the voltage, the pressure and/or the volumetric flow for the plasma gas (PG1, PG2) and/or the auxiliary gas (SG) with which the operation of the plasma torch (1) can be controlled and/or regulated.

5. Plasma torch according to any of the claims 1 to 4, characterized in that a further feed (36) for a Secondary Gas (SG) is led outside through the housing (30) and through a nozzle-protecting cap (25) and a gas guide (23) formed in the nozzle-protecting cap (25) close to a plasma jet, which emerges through the nozzle opening (210), a valve (55) being connected to the further feed (36) for the Secondary Gas (SG).

6. Plasma torch according to any of the claims 1 to 4, characterized in that, in addition to the valve (33) present at the hollow space (11), inside the housing (30) before the connection to the hollow space (11) at the respective feeds (34, 35), in the flow direction of the respective plasma gas (PG1, PG2), there is arranged at least one valve (31, 32) for opening and closing the feeds (34, 35) for plasma gas (PG1, PG 2).

7. Plasma torch according to claim 6, characterized in that the valves (31, 32, 33) arranged within the housing (30) are actuated electrically, pneumatically or hydraulically.

8. Plasma torch according to claim 6, characterized in that the valves (31, 32, 33) arranged within the housing (30) are formed as axial valves.

9. Plasma torch according to claim 6, characterized in that at least one valve (31, 32, 33) arranged in the housing (30) has a maximum outer diameter or a maximum average facing angle line of 15mm and/or has a maximum length of 50mm and/or the housing (30) has a maximum outer diameter of 52 mm; and/or the maximum outer diameter of at least one valve (31, 32, 33) arranged in the housing (30) is at most 1/4 of the outer diameter or the maximum average facing angle of the housing (30), and/or the at least one valve (31, 32, 33) arranged in the housing (30) has a maximum electrical power consumption of 10W.

10. Plasma torch according to claim 6, characterized in that at least one valve (31, 32, 33) arranged in the housing (30) has a maximum outer diameter or a maximum average facing angle of maximum 11 mm.

11. Plasma torch according to claim 6, characterized in that at least one valve (31, 32, 33) arranged in the housing (30) has a maximum length of at most 40 mm.

12. Plasma torch according to claim 11, characterized in that at least one valve (31, 32, 33) arranged in the housing (30) has a maximum length of at most 30 mm.

13. Plasma torch according to claim 9, characterized in that the maximum outer diameter of at least one valve (31, 32, 33) arranged in the housing (30) is at most 1/5 of the outer diameter or the maximum average facing angle line of the housing (30).

14. Plasma torch according to claim 6, characterized in that at least one valve (31, 32, 33) arranged in the housing (30) has a maximum electrical power consumption of 3W.

15. Plasma torch according to claim 6, characterized in that at least one valve (31, 32, 33) arranged in the housing (30) has a maximum electrical power consumption of 2W.

16. Plasma torch according to claim 6, wherein in the electrically operable valves (31, 32, 33) the plasma gas (PG1, PG2) and/or the auxiliary gas (SG) flow through the windings of the coil (S).

17. Plasma torch according to claim 6, characterised in that the hollow space (11) has a reduced free cross section in the flow direction before the valve (33) at the opening of the hollow space (11) and/or that the opening at the hollow space (11) has a reduced free cross section in the flow direction after the valve (33) at the opening of the hollow space (11), or that a membrane reducing the free cross section is arranged in the hollow space (11) before the valve (33) at the opening of the hollow space (11) or in the opening of the hollow space (11) after the valve (33) at the opening of the hollow space (11).

18. A plasma torch according to any of the claims 1 to 4, characterized in that it is formed as a fast-changing torch with a plasma torch shaft (3) separable from the plasma torch head (2).